Chicago police said the 17-year-old boy, Davion Pryor, shot Tatanisha Jackson, 43, on Thursday afternoon in the 6800 block of South Cornell Avenue while their family members were watching.
The teen has now been charged as an adult with first degree murder in connection to the slaying.
Dressed in an orange juvenile detention shirt and jeans, Pryor appeared in court Saturday, where new details were revealed in the murder case.
Pryor is accused of pulling out a gun and shooting his mother in the head four times in front of the teen's father and 7-year-old brother, who they'd just picked up from school.
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During the hearing, authorities said before the family arrived home, the teen had called his mother to talk to her about someone drinking alcohol on the back porch.
The teen's father and brother, who witnessed the attack, told police it was as Tatanisha unlocked the home's front door when Pryor opened the door and then pointed a gun at his mother and opened fire at nearly point-blank range. She was shot in the head four times.
Prosecutors said the father picked up his younger son and ran to safety ,where he called 911. They said they then heard five more gunshots from inside the home.
Police said the teen ran off after the shooting through the apartment's back door. He was captured on security cameras along Stoney Island and his cellphone pinged in the area.
He later turned himself in that same day at the at the 3rd District police station. He was arrested at 9:59 p.m. in the 7000 block of South Cottage Grove. A 9-millimeter gun used in the attack and 12 bullet casings were recovered from the scene, police said.
Authorities said at the time of the murder, Pryor was already on home confinement after being charged as a juvenile with aggravated battery after being found guilty of a carjacking in July.
An attorney for the teen said in court Saturday that he was in a GED program and had a part time job.
Cook County Judge David Kelly called the attack unprovoked and unjustified, ordering the teen to remain behind bars.
"This is very sad and tragic to this court..." Kelly said. "The unprovoked shooting and killing of your mother in front of your father and brother."
Relatives of the teen left court Saturday without comment.
The court has ordered a mental health evaluation for Pryor, who is due back in court next week.
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